The document discusses the passive voice in English grammar. It explains that the passive voice is used when the focus is on the action rather than the performer, or when the performer is unknown. It provides examples of changing sentences from active to passive voice by making the object the subject and using the verb "to be" plus the past participle. The tense must match between the main verb and the form of "to be" used. Various examples are given for changing sentences between active and passive voice in simple present, present progressive, present perfect, and simple past tenses.